Our fundamental goals in this project are: (1) to understand the mechanisms operative in the absorption, utilization, storage, and excretion of trace metals by mammalian systems with particular interest to iron metabolism; and (2) to apply this understanding to the detection and prevention of pathological and nutritional disorders of iron metabolism. Our research methods include a physical-chemical characterization of the solution chemistry of polymeric iron. We will determine the size and shape of these polymers by techniqes of ultracentrifugation and gel- permeation. Their structure and colloidal properties will be defined by spectral, magnetic, and electrophoretic characterization; their interaction with stabilizing ligands will also be investigated. The interaction of iron with phosphorylserine residues of phosvitin and caseins will be examined to establish the basis for inhibition of iron absorption by phosphoproteins of dietary origin. We will use the results of our physical-chemical investigations to design rational and expeditious methods for facilitating the absorption of dietary and therapeutic levels of iron. Assimilbility of orally administered iron compounds will be asessed by measurement of whole-body retention of radioactive iron, by measurement of liver ferritin iron stores, and by analyzing hematological responses.